This macro can automatically implement the TryFromliteral
must be only one type
```rust use literal_enum::LiteralEnum;
enum Command { /// increment pointer #[lit = b'>'] IncrementPointer, // > /// decrement pointer #[lit = b'<'] DecrementPointer, // < }
let b = b'>'; let cmd = Command::try_from(b).unwrap(); assert!(matches!(cmd, Command::IncrementPointer));
let b: u8 = cmd.into(); assert_eq!(b, b'>'); ```